关于切换jbutton背景图片问题，专家请进！

            jbutton.addmouselistener（new java.awt.event.mouseadapter（) {
                public void mouseentered（java.awt.event.mouseevent e) {
                    jbutton.seticon（new imageicon（this.getclass（).getresource（"images/1.gif")));   // 添加图片             
}
            });

import java.awt.borderlayout;
import java.awt.event.mouseevent;
import java.awt.event.mouselistener;
import javax.swing.imageicon;
import javax.swing.jbutton;
import javax.swing.jframe;

public class test implements mouselistener {
    jframe jf;

    jbutton jb1, jb2;

    public static void main（string[] args) throws exception {
        new test（).go（);
    }

    public void go（) {
        jf = new jframe（);
        jb1 = new jbutton（);
        jb2 = new jbutton（);
        jb1.addmouselistener（this);
        jf.add（jb1, borderlayout.north);
        jf.add（jb2, borderlayout.south);
        jf.setvisible（true);
        jf.setsize（400, 200);
        jf.setdefaultcloseoperation（jframe.exit_on_close);
    }

    public void mouseclicked（mouseevent e) {
        // todo auto-generated method stub

    }

    public void mouseentered（mouseevent e) {
        jb1.seticon（new imageicon（this.getclass（).getresource（"1.jpg")));
    }

    public void mouseexited（mouseevent e) {
        jb1.seticon（new imageicon（this.getclass（).getresource（"2.jpg")));
    }

    public void mousepressed（mouseevent e) {
        // todo auto-generated method stub

    }

    public void mousereleased（mouseevent e) {
        // todo auto-generated method stub

    }

}